Ligand compound, catalyst system for olefin oligomerization, and method for olefin oligomerization using the same

ABSTRACT

This disclosure relates to a novel ligand compound that can oligomerize ethylene with high catalyst activity and selectivity, a catalyst system for olefin oligomerization including the same, and a method for olefin oligomerization using the same.

TECHNICAL FIELD

The present invention relates to a ligand compound, a catalyst systemfor olefin oligomerization, and a method for olefin oligomerizationusing the same.

BACKGROUND OF ART

Linear alpha-olefins are important materials used as comonomers,cleaners, lubricants, plasticizers, and the like, and are widely usedindustrially. Particularly, 1-hexene and 1-octene are used as comonomersfor controlling the density of polyethylene when preparing linear lowdensity polyethylene (LLDPE).

In the conventional preparation process of LLDPE, copolymerization withcomonomers such as alpha-olefins, for example, 1-hexene and 1-octene, isconducted so that a branch may be formed in the polymer backbonetogether with ethylene to control the density.

Thus, in order to prepare LLDPE with high comonomer content, there is aproblem in that the cost of comonomers accounts for a great part of theproduction cost. Various attempts have been made in order to overcomethis problem.

Since alpha-olefins have different application fields or market fieldsaccording to the kind, technologies capable of selectively producingspecific olefins is commercially important, and recently, many studieshave progressed on chromium catalyst technology for preparing 1-hexeneor 1-octene with high selectivity through selective ethyleneoligomerization.

Existing commercial methods for preparing 1-hexene or 1-octene includethe SHOP process of Shell Chemical, the Ziegler process of ChevronPhilips, and the like, which may be used to produce a wide distributionof alpha-olefins ranging from C4-20.

As a trimerization catalyst of ethylene, a chromium-based catalyst usinga ligand of general formula (R1)(R2)X—Y—X(R3)(R4) has been suggested. Inthe formula, X is phosphorus, arsenic, or antimony, Y is a linking groupsuch as —N(R5)-, and at least one of R1, R2, R3, and R4 has a polar orelectron accepting substituent.

A representative example of such ligands is(o-ethylphenyl)₂PN(Me)P(o-ethylphenyl)₂, which is a compound wherein atleast one of R1, R2, R3, and R4 does not have a polar substituent (Chem.Commun., 2002, 858).

However, there is continued demand for development of ligands that havecontinuously continued oligomerization activity and high selectivitywhen preparing 1-octene or 1-hexene.

PRIOR ART DOCUMENT Non-Patent Documents

-   1. Chem. Commun., 2002, 858

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

It is the object of the invention to provide a ligand compound that canoligomerize ethylene with high catalytic activity and selectivity, acatalyst system for olefin oligomerization including the same, and amethod for olefin oligomerization using the same.

Technical Solution

A ligand compound according to one aspect of the invention may berepresented by the following Chemical Formula 1.

In Chemical Formula 1,

X is R₁—N, O, or S,

R₁ is a C1-20 alkyl group, a C6-40 aryl group, a C3-30 heteroaryl group,an arylalkyl group, optionally containing at least one heteroatomselected from N, O, F, S, and P, or hydrogen,

R₂ to R₅ are independently a C6-40 aryl group, and

R₆ and R₇ are H or a C1-20 alkyl group.

A catalyst system for olefin oligomerization according to another aspectof the invention may include a ligand compound represented by thefollowing Chemical Formula 1, a chromium source, and a cocatalyst.

In Chemical Formula 1,

X is R₁—N, O, or S,

R₁ is a C1-20 alkyl group, a C6-40 aryl group, a C3-30 heteroaryl group,an arylalkyl group, optionally containing at least one heteroatomselected from N, O, F, S, and P, or hydrogen,

R₂ to R₅ are independently a C6-40 aryl group, and

R₆ and R₇ are H or a C1-20 alkyl group.

A method for olefin oligomerization according to yet another aspect mayinclude the step of oligomerizing olefins in the presence of a catalystsystem for olefin oligomerization including a ligand compoundrepresented by the following Chemical Formula 1, a chromium source, anda cocatalyst.

In Chemical Formula 1,

X is R₁—N, O, or S,

R₁ is a C1-20 alkyl group, a C6-40 aryl group, a C3-30 heteroaryl group,an arylalkyl group, optionally containing at least one heteroatomselected from N, O, F, S, and P, or hydrogen,

R₂ to R₅ are independently a C6-40 aryl group, and

R₆ and R₇ are H or a C1-20 alkyl group.

Advantageous Effects

By using the catalyst system including the ligand compound according tothe present invention, ethylene can be oligomerized with highselectivity compared to the existing catalyst system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Although various modifications may be made in the present invention, andthe present invention may have various embodiments, specific embodimentswill be explained in detail in the specification. However, it is to beunderstood that the present invention is not limited to specificembodiments, and covers all modifications, equivalents, and alternativesfalling within the spirit and the scope of the invention. If it isjudged that detailed explanations regarding related known technologiesmay obscure the subject matter of the invention, the detailedexplanations will be omitted.

The present invention provides a ligand compound represented by thefollowing Chemical Formula 1.

[Chemical Formula 1]

In Chemical Formula 1,

X is R₁—N, O, or S,

R₁ is a C1-20 alkyl group, a C6-40 aryl group, a C3-30 heteroaryl group,an arylalkyl group, optionally containing at least one heteroatomselected from N, O, F, S, and P, or hydrogen,

R₂ to R₅ are independently a C6-40 aryl group, and

R₆ and R₇ are H or a C1-20 alkyl group.

According to another aspect of the invention, a catalyst systemincluding the ligand compound represented by Chemical Formula 1, achromium source, and a cocatalyst is provided.

According to yet another aspect of the invention, a method for olefinoligomerization including the step of oligomerizing olefins in thepresence of a catalyst system for olefin oligomerization including aligand compound represented by Chemical Formula 1, a chromium source,and a cocatalyst is provided.

The catalyst for olefin oligomerization of the prior art has a problemin that it does not have high oligomerization activity and highselectivity. Thus, the inventors confirmed through experiments that if acatalyst system including the novel ligand compound is used, higholigomerization activity and high selectivity may be consistentlymaintained in olefin oligomerization, and completed the invention.

Hereinafter, a ligand compound, a catalyst system for olefinoligomerization, and a method for olefin oligomerization using the sameaccording to the present invention will be explained detail.

Ligand Compound

The ligand compound of the present invention may be represented by thefollowing Chemical Formula 1.

In Chemical Formula 1,

X is R₁—N, O, or S,

R₁ is a C1-20 alkyl group, a C6-40 aryl group, a C3-30 heteroaryl group,an arylalkyl group, optionally containing at least one heteroatomselected from N, O, F, S, and P, or hydrogen,

R₂ to R₅ are independently a C6-40 aryl group, and

R₆ and R₇ are H or a C1-20 alkyl group.

More specifically, according to one embodiment of the invention,examples of the ligand compound represented by Chemical Formula 1 may berepresented by one of the following structural formulae, but are notlimited thereto. The following compounds may be prepared by a commonmethod for preparing a ligand, and will be explained in more detail inexamples below.

The compound represented by Chemical Formula 1 may be synthesized by thefollowing method, but is not limited thereto.

Catalyst System for Olefin Oligomerization

The catalyst system for olefin oligomerization according to the presentinvention may include a ligand compound represented by the followingChemical Formula 1; a chromium source; and a cocatalyst.

In Chemical Formula 1,

X is R₁—N, O, or S,

R₁ is a C1-20 alkyl group, a C6-40 aryl group, a C3-30 heteroaryl group,an arylalkyl group, optionally containing at least one heteroatomselected from N, O, F, S, and P, or hydrogen,

R₂ to R₅ are independently a C6-40 aryl group, and

R₆ and R₇ are H or a C1-20 alkyl group.

In the catalysts system for olefin oligomerization of the presentinvention, a “catalyst system” means that the compound represented byChemical Formula 1 and a cocatalyst are simultaneously or sequentiallyadded in any suitable solvent in the presence/absence of monomers, andcan be obtained as an active catalyst composition.

According to one embodiment of the invention, the chromium source may bechromium or a chromium precursor. Specific examples of the chromium orchromium precursor may be chromium (III) acetylacetonoate,tris(tetrahydrofuran)chromium trichloride, or chromium(III)-2-ethylhexanoate, but is not limited thereto.

The catalyst system for olefin oligomerization includes a cocatalyst.The cocatalyst is an organic metal compound containing a Group 13 metal,and in general, is not specifically limited as long as it can be usedfor oligomerization of an olefin in the presence of a transition metalcatalyst.

Specifically, the cocatalyst may be at least one selected from the groupconsisting of compounds represented by the following Chemical Formulae 2to 4, but is not limited thereto.

[Al(R⁶)—O]c-  [Chemical Formula 2]

In Chemical Formula 2, R⁶'s are identical to or different from eachother, and are independently a halogen radical, a C1-20 hydrocarbylradical, or a C1-20 hydrocarbyl radical substituted with a halogen, andc is an integer equal to or greater than 2.

D(R⁷)₃  [Chemical Formula 3]

In Chemical Formula 3,

D is aluminum or boron, and R⁷'s are independently a C1-20 hydrocarbylor a C1-20 hydrocarbyl substituted with a halogen.

[L-H]⁺[Q(E)₄]⁻  [Chemical Formula 4]

In Chemical Formula 4,

L is neutral Lewis base, [L-H]⁺ is a Bronsted acid, Q is boron oraluminum in a +3 oxidation state, and E's are independently a C6-20 arylgroup or a C1-20 alkyl group, at least one hydrogen of which isunsubstituted or substituted with a halogen, a C1-20 hydrocarbyl, analkoxy functional group, or a phenoxy functional group.

Examples of the compound represented by Chemical Formula 2 may includemethylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane,butylaluminoxane, and the like.

Examples of the alkyl metal compound represented by Chemical Formula 3may include trimethylaluminum, triethylaluminum, triisobutylaluminum,tripropylaluminum, tributylaluminum, dimethylchloroaluminum,dimethylisobutylaluminum, dimethylethylaluminum, diethylchloroaluminum,triisopropylaluminum, tri-s-butylaluminum, tricyclopentylaluminum,tripentylaluminum, triisopentylaluminum, trihexylaluminum,ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminumtri-p-tolylaluminum, dimethylaluminummethoxide,dimethylaluminumethoxide, trimethylboron, triethylboron,triisobutylboron, tripropylboron, tributylboron, and the like.

Examples of the compound represented by Chemical Formula 4 may includetriethylammoniumtetraphenylboron, tributylammoniumtetraphenylboron,trimethylammoniumtetraphenylboron, tripropylammoniumtetraphenylboron,trimethylammoniumtetra(p-tolyl)boron,tripropylammoniumtetra(p-tolyl)boron,triethylammoniumtetra(o,p-dimethylphenyl)boron,trimethylammoniumtetra(o,p-dimethylphenyl)boron,tributylammoniumtetra(p-trifluoromethylphenyl)boron,trimethylammoniumtetra(p-trifluoromethylphenyl)boron,tributylammoniumtetrapentafluorophenylboron,N,N-diethylaniliniumtetraphenylboron,N,N-diethylaniliniumtetraphenylboron,N,N-diethylaniliniumtetrapentafluorophenylboron,diethylammoniumtetrapentafluorophenylboron,triphenylphosphoniumtetraphenylboron,trimethylphosphoniumtetraphenylboron,triethylammoniumtetraphenylaluminum,tributylammoniumtetraphenylaluminum,trimethylammoniumtetraphenylaluminum,tripropylammoniumtetraphenylaluminum,trimethylammoniumtetra(p-tolyl)aluminum,tripropylammoniumtetra(p-tolyl)aluminum,triethylammoniumtetra(o,p-dimethylphenyl)aluminum,tributylammoniumtetra(p-trifluoromethylphenyl)aluminum,trimethylammoniumtetra(p-trifluoromethylphenyl)aluminum,tributylammoniumtetrapentafluorophenylaluminum,N,N-diethylaniliniumtetraphenylaluminum,N,N-diethylaniliniumtetrapentafluorophenylaluminum,diethylammoniumtetrapentafluorophenylaluminum,triphenylphosphoniumtetraphenylaluminum,trimethylphosphoniumtetraphenylaluminum,triphenylcarboniumtetraphenylboron,triphenylcarboniumtetra(p-trifluoromethylphenyl)boron,triphenylcarboniumtetrapentafluorophenylboron, and the like.

Preferably, an alumoxane may be used, and more preferably, analkylalumoxane such as methylalumoxane (MAO) may be used.

According to one embodiment of the invention, the catalyst system forolefin oligomerization may include the ligand compound represented byChemical Formula 1, a chromium source, and a cocatalyst. Herein, inorder to increase selectivity to linear alpha olefins and increaseoligomerization activity, the mole ratio of the ligand compound:chromiumsource:cocatalyst may be about 1:1:1 to about 10:1:10,000, preferablyabout 1:1:100 to about 5:1:3,000, but is not limited thereto.

In a catalyst system including the ligand compound represented byChemical Formula 1, a chromium source, and a cocatalyst, the threecomponents of the catalyst system may be added simultaneously orsequentially and in any order in any suitable solvent in the presence orabsence of monomers and obtained as an active catalyst. The suitablesolvent may include heptanes, toluene, 1-hexene, diethylether,tetrahydrofuran, acetonitrile, dichloromethane, chloroform,chlorobenzene, methanol, acetone, and the like, but is not limitedthereto.

By using the catalyst system according to the present invention, amethod for olefin oligomerization with improved reaction activity andselectivity may be provided.

Method for Olefin Oligomerization

The method for olefin oligomerization according to the present inventionmay include the step of oligomerizing olefins in the presence of acatalyst system for olefin oligomerization including a ligand compoundrepresented by the following Chemical Formula 1, a chromium source, anda cocatalyst.

In Chemical Formula 1,

X is R₁—N, O, or S,

R₁ is a C1-20 alkyl group, a C6-40 aryl group, a C3-30 heteroaryl group,an arylalkyl group, optionally containing at least one heteroatomselected from N, O, F, S, and P, or hydrogen,

R₂ to R₅ are independently a C6-40 aryl group, and

R₆ and R₇ are H or a C1-20 alkyl group.

According to one embodiment of the invention, an olefin oligomer may beprepared by a homogeneous liquid phase reaction, a slurry reactionwherein a part of or the whole catalyst system is not dissolved, atwo-phase liquid/liquid reaction, or a bulk phase reaction whereinproduct olefin acts as a main medium, or a gas phase reaction, in thepresence or absence of in inert solvent using the catalyst systemaccording to above-explained embodiment and a common device and contacttechnology, but the homogeneous liquid phase reaction is preferable.

The olefin oligomerization may be conducted in any inert solvent thatdoes not react with a catalyst compound and an activator. Suitable inertsolvents may include benzene, toluene, xylene, cumene, heptanes,cyclohexane, methylcyclohexane, methylcyclopentane, hexane, pentane,butane, isobutene, and the like, but are not limited thereto. Herein,according to one embodiment of the invention, the solvent may be treatedwith a small amount of alkyl aluminum to remove a small amount of wateror air and the like that act as a catalyst poison.

According to one embodiment of the invention, the olefin oligomerizationmay be conducted at a temperature of about 5 to about 200° C.,preferably about 30 to about 150° C.

According to one embodiment of the invention, the olefin oligomerizationmay be conducted at a pressure of about 1 to about 300 bar, preferablyabout 2 to about 150 bar.

When conducting olefin oligomerization using a catalyst system, if theabove-explained compound or a catalyst system including the sameaccording to the present invention is used, high selectivity to 1-hexeneand 1-octene may be achieved.

Hereinafter, preferable examples of the invention will be explained indetail. However, these examples are only to illustrate the invention,and the scope of the invention is not limited thereto.

Synthesis of Ligand Compound Synthesis Example

All the reactions were progressed under argon using the Schlenktechnique or a glove box. The synthesized ligand was analyzed by ¹H (500MHz) and ³¹P (202 MHz) NMR spectra using a Varian 500 MHz spectrometer.The shift was expressed in ppm, downfield from TMS with the residualsolvent peak as reference. A phosphorous probe was calibrated withaqueous H₃PO₄. Under Ar, amine (10 mmol) and triethylamine (3˜10 equiv.to amine) were dissolved in dichloromethane (80 mL). While the flask wasimmersed in a water bath, chlorodiphenylphosphine (20 mmol) was slowlyadded thereto, and agitated overnight. After evaporation of the solventunder vacuum, other solvents (diethyl ether, tetrahydrofuran, or hexane)were added thereto and sufficiently agitated, and triethylammoniumchloride salt was removed with an air-free glass filter. The solvent wasremoved from the filtrate to obtain a product. The starting amines forpreparing the ligands used in examples and comparative examples areshown in the following Table 1.

TABLE 1 Synthesis Example Starting amine Ligand Synthesis Example 11-Benzyl-3- aminopyrrolidine

Synthesis Example 2 3-amino- tetrahydrofuran HCl

Synthesis Example 3 cis-3-Amino- 1-benzyl-2- methylpyrrolidine

Synthesis Example 4 2-aminopropane

Ethylene Oligomerization Example 1

Under argon gas, Cr(acac)₃ (17.5 mg, 0.05 mmol) and the ligand 1 (0.1mmol) prepared according to Synthesis Example 1 were put in a flask, 10ml of toluene was added, and the mixture was agitated to prepared a 5 mMsolution.

A magnetic stir bar was put into a 100 mL Parr reactor and assembled,and then the inside was placed under vacuum (for at least 2 hours).After replacing the inside with Ar, 46 mL of cyclohexane and 2 mL of MAO(10 wt % toluene solution, Al/Cr=300) were injected. 2 mL (10 μmol) of a5 mM catalyst solution (toluene) was injected into the reactor. Thereactor was immersed in an oil bath heated to 45° C., and connected withan ethylene supply. The pressure of ethylene was adjusted to 45 bar, andagitation began at 600 rpm. After 15 minutes of reaction, the ethylenewas cut off, and the reactor was taken out and cooled with a dryice/acetone bath. After venting, the reactor was opened and 0.5 mL ofnonane (GC internal standard) was added thereto. About 2 mL of theliquid part was taken and quenched with water, and the organic part wasfiltered with a PTFE syringe filter to prepare a GC sample. Thedistribution of the liquid product was analyzed with GC. To theremaining reaction solution, 300 mL of ethanol/HCl (10 vol %) was added,and the solution was agitated and filtered to obtain a polymer. Thepolymer was dried overnight in a vacuum oven at 65° C.

Example 2

Ethylene oligomerization was conducted by the same method as Example 1,except that the ligand prepared according to Synthesis Example 2 wasused.

Example 3

Ethylene oligomerization was conducted by the same method as Example 1,except that the ligand prepared according to Synthesis Example 3 wasused.

Comparative Example 1

Ethylene oligomerization was conducted by the same method as Example 1,except that the ligand prepared according to Synthesis Example 4 wasused, and methylcyclohexane was used as a reaction solvent.

The results of Examples 1 to 3 and Comparative Example 1 are summarizedin the following Table 2.

TABLE 2 Activity 1-C₆ 1-C₈ Sum (kg/molCr/hr) (wt %) (wt %) (wt %)Comparative 980 16.3 52.5 68.8 Example Example 1 844 15.1 61.0 76.1Example 2 1410 20.5 51.2 71.7 Example 3 380 30.6 54.1 84.7

As shown in Table 2, in the examples, selectivity to 1-hexene and1-octene was remarkably improved compared to the comparative example.

Although specific parts of the invention have been described in detail,it would be obvious to one of ordinary knowledge in the art that suchspecific technologies are no more than preferable embodiments, and thescope of the invention is not limited thereto. Thus, the scope of theinvention is defined by the attached claims and equivalents thereof.

1-2. (canceled)
 3. A catalyst system for olefin oligomerization,comprising: a ligand compound represented by the following ChemicalFormula 1; a chromium source; and a cocatalyst:

wherein, in Chemical Formula 1, X is R₁—N, O, or S, R₁ is a C1-20 alkylgroup, a C6-40 aryl group, a C3-30 heteroaryl group, an arylalkyl group,optionally containing at least one heteroatom selected from N, O, F, S,and P, or hydrogen, R₂ to R₅ are independently a C6-40 aryl group, andR₆ and R₇ are H or a C1-20 alkyl group.
 4. The catalyst system accordingto claim 3, wherein the ligand compound represented by Chemical Formula1 is selected from the group consisting of


5. The catalyst system according to claim 3, wherein the chromium sourceis selected from the group consisting of chromium (III)acetylacetonoate, tris(tetrahydrofuran)chromium trichloride, andchromium (III)-2-ethylhexanoate.
 6. The catalyst system according toclaim 3, wherein the cocatalyst is at least one selected from the groupconsisting of compounds represented by the following Chemical Formulae 2to 4:—[Al(R⁶)—O]c-  [Chemical Formula 2] wherein, in Chemical Formula 2, R⁶'sare identical to or different from each other, and are independently area halogen radical, a C1-20 hydrocarbyl radical, or a C1-20 hydrocarbylradical substituted with a halogen, and c is an integer equal to orgreater than 2,D(R⁷)₃  [Chemical Formula 3] wherein, in Chemical Formula 3, D isaluminum or boron, R⁷'s are independently a C1-20 hydrocarbyl or a C1-20hydrocarbyl substituted with a halogen, and[L-H]⁺[Q(E)₄]⁻  [Chemical Formula 4] wherein, in Chemical Formula 4, Lis a neutral Lewis base, [L-H]⁺ is a Bronsted acid, Q is boron oraluminum in a +3 oxidation state, E's are independently a C6-20 arylgroup or a C1-20 alkyl group, at least one hydrogen of which isunsubstituted or substituted with a halogen, a C1-20 hydrocarbyl, analkoxy functional group, or a phenoxy functional group.
 7. The catalystsystem according to claim 3, wherein the olefin is ethylene. 8-12.(canceled)